Merge Two Sorted Linked Lists Java Program - The Coding Shala

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Merge Two Sorted Linked Lists Java Program

Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.

Example:

Input: 1->2->4, 1->3->4

Output: 1->1->2->3->4->4

Merger two Sorted Linked Lists Java Program

Approach 1:
Using iterative. We can make a new Linked list.

Java Code

```/**
* public class ListNode {
*     int val;
*     ListNode next;
*     ListNode(int x) { val = x; }
* }
*/
class Solution {
public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
if(l1 == null && l2 == null) return null;
if(l1 == null) return l2;
if(l2 == null) return l1;
ListNode dummy = new ListNode(0);
while(l1 != null && l2 != null){
if(l1.val <= l2.val){
dummy.next = l1;
l1 = l1.next;
}else{
dummy.next = l2;
l2 = l2.next;
}
dummy = dummy.next;
}
if(l1 != null) dummy.next = l1;
if(l2 != null) dummy.next = l2;
}
}
```

Approach 2:
Recursive method.

Java Code

```/**
* public class ListNode {
*     int val;
*     ListNode next;
*     ListNode(int x) { val = x; }
* }
*/
class Solution {
public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
if(l1 == null) return l2;
if(l2 == null) return l1;
if(l1.val < l2.val){
l1.next = mergeTwoLists(l1.next, l2);
return l1;
}else{
l2.next = mergeTwoLists(l1, l2.next);
return l2;
}
}
}
```

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